Method of making ultrafine wc-co alloys

Abstract

The present invention relates to a method of making ultrafine WC—Co alloys from a well dispersed mixture of fine and non-agglomerated WC and Co powders, wherein the Co powders have a narrow grain size distribution wherein at least 80% of the grains have sizes in the interval x+0.2x with the interval of variation of 0.4x is not smaller than 0.1 um, and a carbon content of approximately the amount necessary to provide eta phase formation.

What is claimed is:  
     
       1. A method of making a cemented carbide having a submicron WC grain size, the method comprising the steps of: 
       (i) forming a powder mixture comprising deagglomerated submicron WC produced by carbothermal reaction, Co powder having deagglomerated spherical grains of submicron size with a narrow grain size distribution wherein at least 80% of the grains have sizes in the interval x+0.2x with the interval of variation of 0.4x is not smaller than 0.1 μm, a carbon content of approximately the amount necessary to provide eta phase formation, and <1 wt. % grain growth inhibitor;  
       (ii) milling the powder mixture; and  
       (iii) sintering.  
     
     
       2. Method according to  claim 1  adding the VC and Cr 3 C 2  in such proportions that the ratio VC/Cr 3 C 2  in wt-% is between 0.33-1.0 for PCB-applications and 0-0.5 for metal cutting. 
     
     
       3. The method of  claim 1 , wherein the cemented carbide has an average grain size of <0.8 μm, with essentially no grains larger than 1.5 μm. 
     
     
       4. The method of  claim 1 , wherein the cemented carbide has 6-24 wt. % Co. 
     
     
       5. The method of  claim 1 , wherein the grain growth inhibitor comprises at least one of VC and Cr 3 C 2 . 
     
     
       6. The method of  claim 1 , wherein the spherical Co grains have an average grain size of approximately 0.4 μm. 
     
     
       7. The method of  claim 1 , wherein the Co powder is polyol cobalt. 
     
     
       8. The method of  claim 1 , wherein the sintering comprises HIP-sintering at a temperature <1400° C. 
     
     
       9. The method of  claim 2 , wherein the ratio is 0.5-0.9. 
     
     
       10. The method of  claim 2 , wherein the ratio is 0.7-0.8. 
     
     
       11. The method of  claim 2 , wherein the ratio is 0.0-0.5. 
     
     
       12. The method of  claim 1 , wherein the cemented carbide has 5-8 wt. % Co. 
     
     
       13. The method of  claim 1 , wherein the cemented carbide has 2-5 wt. % Co. 
     
     
       14. The method of  claim 1 , wherein the cemented carbide has an average grain size <0.4 μm. 
     
     
       15. A cemented carbide cutting tool made by the process of  claim 1 . 
     
     
       16. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight %, 6-10% Co, 0.0-0.3% VC, 0.3-0.75% Cr 3 C 3  and the remainder WC having a grain size <0.8 μm. 
     
     
       17. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight %, 10-16% Co, 0.5-1.2% Cr 3 C 3  and the remainder WC having a grain size <0.8 μm. 
     
     
       18. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight %, 16-20% Co, 0.8-1.8% Cr 3 C 3  and the remainder WC having a grain size <0.8 μm. 
     
     
       19. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight %, 5-8% Co, 0.1-0.6% VC, 0.25-0.6% Cr 3 C 3  and the remainder WC having a grain size <0.4 μm. 
     
     
       20. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight%, 8-12% Co, 0.2-0.9% VC, 0.4-0.9% Cr 3 C 3  and the remainder WC having a grain size <0.4 μm. 
     
     
       21. The method of  claim 1 , wherein step (i) comprises forming a powder mixture containing, in weight %, 2-5% Co, 0.05-0.2% VC, 0.1-0.25% Cr 3 C 3  and the remainder WC having a grain size <0.4 μm.